Field-strength meter with frequency counter
CR-3000/C was a mobile frequency counter with built-in field-strength
indicator and acoustic feedback,
developed around 1997 by Dare Instruments in Woerden (Netherlands)
 for use by the Dutch
Radio Monitoring Service (RCD) 1
and by the Dutch Police.
The units were used by both services to determine the frequency of a mobile
radio system in close proximity, in order to be able to intercept it.
mainly used it to find clandestine users of the frequency spectrum.
The unit has the form factor of a standard car radio, so that it could be
built into virtually any vehicle, without attracting too much attention.
It is powered by the 12V car battery (10-15V DC).
The CR-3000/C has a frequency range from DC to 1 GHz and will automatically
lock onto the strongest signal when in close proximity of a transmitter.
When locked, the 8-digit display will instantly show the
frequency of the intercepted signal. In the nearfield of the transmitter,
the 8-unit LED bar to the right of the display will give an indication of
the field-strength of that signal.
The device has a 1/100 output — directly from its prescaler — that can be
fed to the PAN-2000 monitoring receiver
that was introduced at the RCD around
the same time. Once the CR-3000/C has locked itself onto a nearby signal, the
displayed frequency can be copied to the PAN-2000 instantly by pressing a
button on its console. The audio signal can then be monitored directly.
It is currently unknown how many CR-3000/C units were made, but assuming that
the RCD had one in every vehicle and that each police district in the Netherlands had between 2 and 4 units, we assume
that between 100 and 200 units were built.
In 1013/2014, the majority was dumped on the Dutch surplus market.
The portable version of the CR-3000 is known as the
At the time known as HDTP-RDR.
All controls are at the front panel of the CR-3000/C, which
consists of an aluminium panel with a custom-made self-adhesive keypad.
At the lower half of the panel are the push-buttons for its
control. At the far left is the ON/OFF button.
The display has two brightness settings – controlled with the DIM button –
one for when the unit is used in bright daylight and one for use at night.
The remaining black buttons (marked with up/down arrows) are for
adjusting the threshold and sensitivity levels of the device,
and for adjusting the volume of the acoustic indicator (known as the rattle).
When a speaker
is connected at the rear, the unit will produce a tone of varying height
depending on the strength of the signal, in parallel with the LED bar
indicator at the front panel.
The image above shows the connectors at the rear of the CR-3000/C.
The power socket accepts a wide range of DC voltages (10-15V) and was
typically connected to the 12V battery of a car. Note that the sockets
for the power input and the speaker output are identical.
Do not swap them,
as connecting power to the speaker output will permanently damage
the audio amplifier.
The 1/100 output is for connection to the
PAN-2000 monitoring receiver
that was used by the RCD.
It allows the PAN-2000 to instantly tune into the
frequency shown on the display of the CR-3000/C.
The interior of the CR-3000/C can be accessed by removing 4 screws from the
sides of the unit. This allows the upper and lower sections of the case to
be separated, after which the interior becomes visible. The image below
shows the interior or the CR-3000/C, as seen from the rear.
The first impression is somewhat disappointing. One would expect a professional
custom-made instrument like this to be a single integrated design, but instead
it consists of a collection of separate PCBs — that were (probably)
designed for other products — that are bolted together.
was clearly designed for, say, an HF instrument, and is bolted
to the bottom of the case. To the left of the front-end is a small PCB that
holds the DC power converter and the audio amplifier.
The main unit, mounted at
the left, consists of three stacked and bolted PCBs.
The upper PCB of the main unit appears to be nothing more than a cable
adapter. The second PCB contains an
Intersil ICM7216D ,
which is an 8-digit LED display driver / frequency counter. Despite the
rather disappointing first impression however, the unit performs very well
and does exactly what it was designed for. It can still be used as
an intercept or measuring device today.
The block diagram below shows how the CR-3000/C works.
The input signal is first amplified with a 2-stage wide band amplifier.
The frequency counter (N) inside the Intersil ICM7216D is suitable for frequencies
between DC and 10 MHz, which is why the input signal has to be divided
by 100 first. This is done by the pre-scaler, of which the output is
available at the rear (1/100).
The output from the pre-scaler is fed into the frequency counter, which
has a built-in driver for the LED display. The output from the font-end
is also fed into a detector that drives the field-strength LED bar indicator
and the acoustic indicator. The latter is also known as the rattle. 1
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